What do you think is supposed to happen when you press <CTRL><prt sc> or <ALT><prt sc>?
Nothing is supposed to "print" like some folks think.
What happens is the entire screen (for PrtSc) of just the active window for (ALT+PrtSc) gets copied to the Windows clipboard.
The screenshot that is on the clipboard can then be pasted (Ctrl-V) into other programs like MS Paint, MS Word, etc.
After you make your screenshot open something like Microsoft Paint, the press Ctrl-V (paste) to paste the contents of the Windows clipboard into Paint, then you can save the image.
Alternatively in MS Paint you could press the Paste button which will paste the contents of the Windows clipboard into Paint:
You can also use the Windows Snipping tool which you can read about here:
Practice a little and you will get the desired results and become an expert screenshooter.